docs: add CI workflow and testing requirements documentation

- Add GitHub Actions CI pipeline with pytest, ruff, mypy
- Expand Tasks.md with implementation tracking and testing criteria
- Update CONTRIBUTING.md with CI requirements
- Add Testing-Requirements.md with coverage thresholds and PR checks

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Docs/Testing-Requirements.md

@@ -0,0 +1,39 @@
+# Testing Requirements
+
+## Coverage Threshold
+
+- **Minimum: 80% line coverage** for all backend code
+- Critical paths (auth, banning, scheduling, API endpoints): **100%**
+
+## CI Enforcement
+
+`.github/workflows/ci.yml` runs pytest with `--cov-fail-under=80`. Build fails if coverage drops below threshold.
+
+## Running Tests Locally
+
+```bash
+cd backend
+pytest --cov=app --cov-report=term-missing
+```
+
+## Coverage Reports
+
+- Terminal: `--cov-report=term-missing`
+- HTML: `--cov-report=html` (output in `htmlcov/`)
+
+## Coverage Badge
+
+Add to README once CI runs successfully:
+
+```md
+[![Coverage](https://codecov.io/gh/<owner>/BanGUI/branch/main/graph/badge.svg)](https://codecov.io/gh/<owner>/BanGUI)
+```
+
+Requires codecov.io integration with repository.
+
+## Writing Tests
+
+- Follow pattern: `test_<unit>_<scenario>_<expected>`
+- Mock external dependencies (fail2ban socket, aiohttp calls)
+- Test happy path AND error/edge cases
+- See `Docs/Backend-Development.md §9` for detailed testing guide